High-speed circuit interrupter



Oct. 8, 1929.

C. LE G. FORTESCUE HIGH SPEED CIRCUIT INTERRUPTER Filed Aug. 17, 1920 8 I A 4 16 1'? EC I- AM 5mm l Differenfia/{y Wound w se WITNESSES: cvmvmveglwovnd J INVENTOR X4621 W Char/es leffb'rie scue ATTO-RN'EY Patented Get. 8, 1929 UNITED STATES PATENT OFFICE CHARLES LE Gr. FOR'IESCUE, OF PITTSBURGH. PENNS "LVAHIA, ASSIGNOF. T0 WEST- INGHOUSE ELECTRIC & MANUFACTURING COMPANY, A GORIOR-ATION OF PENN- SYLVANIA HIGH-SPEED CIRCUIT INTERRUPTER Application filed August 17, 1920. Serial No. 404,206.

the occurrence of short-circuit conditions or 1 upon the attaining of a predetermined value by the current that traverses the interrupter.

A further object of my invention is to provide a device of the above-indicated character that shall be simple and inexpensive to construct and sensitive and reliable in its operation.

Patent No. 1,427,367, granted Aug. 29, 1923, to Charles Le G. Fortcscue and Frederick C. Hanker, and assigned to the esting house Electric & ll [anut'acturing Company, discloses an e-lectromagnet tor a circuit interrupter that has a winding which serves to energize it while conditions in the circuit are .normal and a second winding which serves to so divert the normal flux from an armature ot the electromagnet as to permit the disengage ment thereof from the core member when a short circuit occurs on the interrupter. The release of the armature permits the immediate opening of the circuit interrupter. In practicing my invention, I provide an actuating electromagnet comprising a core member having four arms so disposed as to constitute two magnetic paths that severally have an air gap therein. The armature of the magnet is directly connected to the movable member of the interrupter, and the core member is energized to cause the armature to normally bridge the air gap in one of the magnetic paths.

Two windings are differentially disposed with respect to each other on the portions of gize the two ditl'erential windings.

the core member between the two air gaps and are respectively energized by the potential difference created across the terminals to a reactor in the circuit by reason of the current traversing the same. One winding has a resistor connected in series therewith, and the other winding as a resistor and a reactor connected in series therewith, across the terminals oi the reactor in the main circuit.

The core member may be energized from an external source or may be energized directly from the circuit. The magnetic flux that is created in, the core member normally traverses the armature member and those portions of the core member that are adapted to be 1nfluenced by the two differential windings.

TVhen the current that traverses the reactor in the main circuit increases slowly, the two differential windings on the core member are correspondingly and equally energized by the "potential difference that is created across the terminals of the reactor. Since the vlndings are diiierentially disposed with respect to each other, the magnetic forces that are produced thereby are opposed and thus counterbalance each other.

lVhen the current that traverses the reactor changes quickly, however, the potential difference across the reactor is quickly increased and tends, correspondingly, to quickly ener- The reactor that is connected in series with one of the windings serves, however, to so limit the energization of that winding that the other winding becomes energized to a greater degree. The latter winding is so disposed with respect to the core member as to divert the flux that normally traverses the armature member, to the other path. and thus to render the armature non-responsive to the flux that traverses the core member. The armature member may then be quickly disengaged from the core member by aspring that is mounted on the circuit interrupter for that purpose.

Figure 1 of the accompanying drawings is a diagrammatic view of an electric circuit that includes a device embodying my invention and Fig 9. is a diagrammatic view of a circuit that includes a modified form of the device shown in Fig. 1.

. A circuit 1, that is supplied with energy from a source 2 of electrornotive force, is provided with a circuit interrupter 3 having an actuating electromagnet l.

The electromagnet 4 comprises a core member 5, having an air gap therein that is adapt ed to be bridged by a movable armature memher 6, and an auxiliary air gap 7 to which the flux may be diverted to permit the release of the armature member. A winding 8 is supplied with c rrent from a source 9 of constant electromotive force for energizing the core member 5. Two windings 10 and 11 are disposed on the portions of the core member between the airgap 7 and the air gap that may be bridged by the armature member 6. The winding 10 is connected in series with a resistor 12 across the terminals of a reactor 13 that is connected in series with the main circuit. The winding 11 is connected in series with an auxiliary reactor let and a resistor 15 across the terminals or" the reactor 13. Q he armature 6 is connected to the movable member 16 of the circuit interrupter 8 and is adapted to be actuated by a spring 17, when it is released by the core member 5.

The two windings 10 and 11 are so difl'erentially disposed with respect to each other that the magnetic forces that are developer thereby neutralize each other. Since the two windings 10 and 11 are connected in parallel across the terminals 01: the reactor 13, it will be understood, of course, that the resistance of the two circuits that include the windings 10 and 11, respectively, should normally be equal. Thus, when the current that traverses the main reactor 13 changes slowly, currents of equal value will be caused to traverse the two windings 10 and 11 and no resultant magnetic effect will be obtained to effect the energization of the core member.

lVhen, however, the current that traverses the reactor 18 changes quickly, the sudden increase in the potential difference across the terminals of the reactor 13, correspondingly, tends to suddenly increase the value of current that traverses thewindings 10 and 11. The impedance of the auxiliary reactor 14, however, is so increased by-the attempted quick change in current therethrough as to limit the current through the windingll. The impedance of the circuit of the winding 10 is not so increased, however, and is therefore increasingly energized in accordance with the increased potential difference across the terminals of the reactor 13.

in reacting upon the normal magnetic flux. that traverses the core member 5 and the ar-;

mature member 6. The magnetic force that 1s developed. by the winding 10 tends to divert the normal flux from the armature member 6, to the auxiliary magnetic path 7, and thereby renders the armature member non responsive to the magnetic flux of the core member. The interrupter 3 is immediately actuated by the force of the spring 17.

The electromagnet 4 that controls the actuation of the interrupter 3 is, therefore, not influenced by fluctuations or slow changes in the current that traverses the circuit, but is very sensitive to quick changes such as are effected upon the occurrence of short-01rcuiting conditions.

The same elements may also be employed with a somewhat different arrangement to eiiect a double result. The windings 10 and 11 may be similarly disposed on the core men ber 5 and similarly connected through resistors 12 and 15 and a reactor l l across the main reactor 13, as illustrated in Fig. 2.

The constants of the cirouit'of the wind ing 10 are such as to cause the winding to be sutliciently energized, only upon a quick change of current through the reactor 13, to divert the flux from the armature member 6 to the auxiliary air gap 7. i

The constants or" the circuit of the wind ing 11 are such that the winding becomes sufficiently energized by the potential drop across the main reactor 13, when the current traversing the same attains a predetermined value. to divert the flux from the an mature member and to permit the disengag ment thereof from the core member.

The resistor 15 1s ad ustable inorder to vary the value of overload at which the wind 11 becomes sufliciently energized to divert the flux from the armature member 6 to per-, mit the disengagement thereof from I the 6018 member With this arrangement of the windings,

the interrupter may be caused to be actuated upon the occurrence of short-circuit conditions or when the circuit current attains a predetermined value.

My invention is not limited to the specific arrangement that is illustrated as modifications may be made therein within the spirit.

and scope of the invention as set forth in the V appended claims.

1 claim as my invention:

1. A quick-acting circuit interrupter mechanism including a magnetizable core member having two magnetic paths, a first means for energizing the core member, a movable armature member for completing one path thereof and a second means torso energizing that path that, normally, the magnetic efiect produced by said second means is nil but, upon the occurrence oi predetermined external conditions, the magnetic flux normally traversing that path and the armature is so shiftd to the other path that the armature member is permitted to be actuated from -the core member. 7

2. A quick-acting circuit interrupter mechanism including a magnetizable core member of substantially U-shape having two magnetic paths, means for energizing the core member, a movable armature member adapted to complete the circuit of one magentic path, two windings disposed between the two magnetic paths and so differentially energized with respect to each other that the magnetic etlect produced thereby, under normal conditions, is nil and, under predetermined conditions, the ell ect of the one winding is so decreased that the magnetic effect of the other winding serves to shift the magnetic flux from the one magnetic path and the movable armature associated therewith, to the other magnetic path.

3. In an electric circuit, the combination with a reactor and a circuit interrupter,quickacting mechanism therefor including a magnetizable core member having two ma netic paths, means for energizing the core member, a movable armautre member associated with one path of the core member, two windings disposed between the two magnetic paths and so normally energized from the reactor, with respect to each other, that the resultant mag netic effect produced thereby is nil for slow changes in the value of the current traversing the reactor and an inductor connected to one of the windings to so limit the value of the current traversing the same upon a sudden change in the current traversing the reactor that the magnetic effect produced by the other winding serves to shift the magnetic flux from the one path and the armature member associated therewith to the other path.

4. In an electric circuit, the combination with a reactor traversed by the circuit current, of a device including a magnetizable core member, a movable armature member re sponsive thereto, means for energizing the core member, means energized from the reactor for contr lling the magnetic flux traversing the armature member, and means associated with one of the controlling means for so limiting the energization thereof, upon a sudden change in the current traversing the reactor, that the other of said controlling means may render the armature member nonresponsive to the core member.

5. In an electric circuit, the combination with a reactor traversed by the circuit current, of a device including two windings energized from the reactor and so disposed with respect to each other that the resultant magnetic elfect produced thereby is nil when the current traversing the reactor varies slowly, and an inductor connected to one winding for so limiting the energization thereof when the current traversing the reactor changes suddenly that the resultant magnetic efiiect produced by the two windings is relatively large.

6. In an electric circuit, the combination with a circuit interrupter, holding means therefor and means for energizing the holding means, of a reactor traversed. by the circuit current, two windings on the holding means energized from the reactor and so disposed as to produce neutralizing eii'ects under normal conditions of slow current variations through the reactor and means for so limiting the effect of one winding when the current traversing the reactor changes suddenly that the other winding is permitted to render the holding means ineffective.

7. A quick-acting interrupter for an elec tric circuit comprising a magnctizable core member for normally engaging an armature member for retaining the circuit interrupter in closed position, means energized from the circuit and so differentially disposed with respect to each other that the forces developed thereby neutralize each other when the current that traverses the circuit changes slowly and means for so controlling one of said circuit-cnergized means upon a sudden increase in the current traversing the circuit as to limit the energization of that means and permit the other means to be increasingly energized in accordance with the increased currents.

8. In an electric circuit, the combination with a reactor in series relation therewith and a circuit interrupter, of means for retaining the circuit interrupter in closed position comprising a holding structure and a core member, vindings on the core member energized from the reactor and so differentially disposed with respect to each other as to produce equal and opposite forces when the current traversing the interrupter changes slowly, and means for limiting the energization of one winding when the current traversing the reactor changes quiclrl; 'nile the other winding is energized in accordance with the increased potential difference across the terminals of the reactor;

9. In combination 'ith an electromagnet having a winding normally energized to re tain a circuit interrupter in closed position, means for releasing said circuit interrupter including a pair of normally balanced windings that are unbalanced only by a rapid change of current through said circuit interrupter.

10. In a combination with a circuit interrupter, a reactor in series therewith, holding magnet for said interrupter ha\ 1g an armature and provided with two cxcr 1g windings connected in shunt relation to said eactor and including circuits having substantially equal resistances but substantiall di'ilerent inductances.

11. A quick-acting interrupter for an electric circuit including a magnetizable core member for normally engaging an armature for retaining the circuit interrupter in closed position, a reactor in the circuit, a plurality of means shunting the reactor and so d1fferentially dlsposed with respect to each other that the forces developed thereby neutralize each other when the current that traverses the circuit changes slowly and means for so controlling one of said means upon a sudden increase in the current traversing the circuit as to limit the energization of that means and permit the other means to be increasingly energized in accordance with the increased currents to cause the armature to be released. In testimony whereof, I have hereunto subscribed my name this 4th day of August, 1920.

CHARLES LE G. FORTESCUE. 

